The present invention relates generally to communication networks such as local area networks (LANs) and particularly concerns a technique for facilitating communications between different LANs.
LANs utilizing various protocols for enabling communications among their constituent stations are generally well known in the art. Among the more common of such protocols are "token ring", "slotted aloha" and carrier sense multiple access with collision detection (CSMA/CD). The interconnection of LANs utilizing different protocol may be effected by a control interface normally referred to as a "gateway", whereas LANs using the same protocol are interconnected by a control interface referred to as a "bridge".
Prior art bridge interfaces commonly comprise so-called memory look-up tables for providing a cross-reference between each station connected to the bridge interface (bridge) and the LAN in which the respective station is situated. More particularly, the memory look-up tables are used to store a plurality of addresses, each identifying a respective station, together with a code identifying the particular LAN to which the station belongs. When a message is directed via the bridge to a given destination station, the memory look-up table is searched to locate the stored address code of the destination station for determining the LAN to which the station belongs. For stations in LANs serviced by different bridges, an interbridge address is created and put in temporary memory when the message is forwarded to the next bridge. The process is repeated for each message, with the bridge directing the message to the appropriate LAN for receipt by the destination station. Return messages are routed through the bridge in a reverse sequence with the temporary addresses being referred to each time. While the foregoing procedure normally operates satisfactorily, the use of such look-up tables and interbridge addresses to effect communications between stations of different LANs is hardware intensive and therefore a relatively costly as well as a low-speed technique.